With all the wet cold weather everyone has had to abandon their Plan A cotton burndown program. So what is the Plan B burndown plan with most wanting to plant cotton around May 1?
There is probably not enough calendar days for the traditional glyphosate plus generic dicamba that has been a staple for us for burndown in cotton. This is because the label on all the generic dicamba formulations ahead of cotton requires a waiting period of 21 days after an inch of rain for the 8 oz/A rate. However in Tennessee, we have a supplemental label for the Clarity formulation of dicamba that lessens the plant back to cotton to 15 days after 1” of rain for the 8 oz/A rate. In theory the 6 less days could make Clarity a viable alternative. However, my understanding is that not much Clarity is sold now and has been replaced with a varied assortment of generics like Sterling Blue, Strut, etc. All those generics are most likely out with respect to plant back interval. Indeed, if the wet weather persists, even if you could source Clarity, the 15 day plant back would be too long to wait before the planters roll.
With so many acres of cotton going to Xtend varieties the obvious choice is to use Engenia or XtendiMax with glyphosate as the burndown and then plant any time after that application. If you go that route please remember that unlike last year, the more stringent label requirements must be followed even if they are applied 30 days before planting. Last year if applications of Engenia or XtendiMax were made 21 or more days before planting you could follow the old dicamba label and use any nozzles, etc. That is no longer the case. For Enlist cotton varieties utilizing Enlist Duo or Enlist One plus glyphosate would be another good burndown option.
A viable option for the new auxin-resistant cotton varieties is to just burndown with glyphosate and then apply Gramoxone plus Cotoran and Caparol behind the press wheel. If horseweeds survive the Gramoxone the regrowth can easily be controlled with the Enlist Duo or Enlist One in Enlist cotton or Engenia or XtendiMax in Xtend cotton. In my mind this strategy makes the most sense as Gramoxone will control any Palmer amaranth that has emerged and we are not exposing pigweed to repeated auxin herbicide applications thus reducing selection pressure for resistance.
Also, Xtend is glufosinate tolerant. In fields near sensitive crops a good plan would be to forgo the dicamba herbicide product and use glufosinate instead. Glufosinate is an outstanding horseweed herbicide but keep in mind, only when air temperatures are in the 80s. Moreover it provides better control when applied in the middle of the day.